Hi Arnd, Sorry for the duplication. Ccing others. On Mon, Jan 20, 2014 at 5:09 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Monday 20 January 2014, Srikanth Thokala wrote: >> On Fri, Jan 17, 2014 at 9:43 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: >> > On Thursday 16 January 2014, Srikanth Thokala wrote: >> > I also assume that some of the properties should just go away: >> > >> > * xlnx,device-id should be the argument in the handle from the slave device >> >> We can have multiple instances of this VDMA IP configured in the FPGA and we >> need a unique identifier for each VDMA device that is present in the FPGA. >> This device-id dt parameter forms the filter mask for the slave devices. As an >> example, this can be used to get a channel of specific VDMA device (assuming >> multiple instances) using the API dma_request_channel(). Please note this >> is an example of a slave device that doesnt have dt node. > > That is not a valid scenario: You should not try to support legacy > slave devices (without DT) connected to a dma-engine that is initialized > using DT. If you still in the progress of converting drivers to DT, you > can use auxdata to attach additional information that can be used for > those slave devices, but the code should be kept out of the mainline > kernel, and I don't want to see it manifest in the bindings. I see your point. Thank you for the clarification. I will fix this in my v2. > >> > * data width should be a property of the slave driver that is configured >> > through dma_slave_config(), unless you can have dma engines that only >> > support certain a width. >> >> Yes, this VDMA engine soft IP support only certain widths, which is >> configurable during IP synthesis. > > But what is this property used for in that case? Surely you can't > connect a slave device to a dmaengine if the bus width doesn't match. > You probably have a point here, but I don't understand it yet. There is a Data-Realignment Engine (DRE) in the IP which is only available for data width setting of 64-bits and less. So, we use the data-width DT parameter to verify this condition and we update alignment shift accordingly. Srikanth > > Arnd > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
